For example when molding a member such as the tread of a tire, a band-shaped member is wound on a molding drum and both longitudinal ends of the band-shaped member are joined to mold the band-shaped member into a cylindrical shape. If the joining is defective, that is, if the longitudinal ends of the band-shaped member cannot be appropriately joined such as when a gap exists between the longitudinal ends, problems such as the thickness of the molded member being not uniform would ensue. In the case where such a joining defect occurs in, for example, the tread of a tire, there is a possibility that the dimensions of the manufactured tire are out of specifications or the tire has poor appearance due to degraded surface quality.
To detect such a joining defect, the positions of the starting end and terminating end of the band-shaped member need to be detected accurately. Patent Literature (PTL) 1 describes the technique of detecting the positions of the starting end and terminating end of the band-shaped member using a two-dimensional laser displacement sensor.